GASTEROPODA. 



119 



Lesson; Lithedaphus Owen; Calyptraea Lam. part.) — 

 Shell conical, cup-shaped, with circular base ; no whorls, 

 but the apex mostly elevated considera- 

 bly ; in the inside hangs an appendage in 

 the shape of a horn, which is open 

 throughout in the front, and fastened on 

 the right side. Animal having between 

 the head and foot a second foot resem- 



Mitnaaria Ddlwynnii. 



bling a prolongation of the mantle ; the 



gills are furnished with short parallel rows of conical 



processes. 



Mitrularia (Calyptraea) equestris is the type of this 

 genus, The animal, according to the discovery of Mr. 

 Cuming, forms a calcareous plate on the place on which it 

 rests its shell, like Hipponyx. Mr. Reeve says on this 

 subject, " Mr. Cuming has lately found at the island of 

 Zebu, one of the Philippines, several specimens of Cali/p- 

 trcea equestris on masses of dead coral about low- water 

 mark, having a testaceous plate attached to the mass, to 

 which the true shell adheres. The edges are finely cre- 

 nulated, and turned up all round, like a platter, as if to 

 protect the margin of the cap-shaped shell which rests 

 within it."* 



Trochita. Schum. (Sigapatella Lesson; Infundibu- 

 lum D'Orb. ; Trochus Lam. part.) — 

 Shell conical, with circular base; the 

 apex nearly central, and having several 

 windings; within there is always a 

 horizontal partition, which may be 

 called a prolongation of the columella. 

 Animal, uniformly pale yellow ; foot 

 obliquely long, equally two-lobed in Trochita. 



* Reeve's Conch. Systematica 



